In a conventional Otto cycle internal combustion (IC) engine, the gasoline fuel is injected into the intake manifold to mix with the air and is drawn into the cylinder through the intake valve during the intake stroke. The fuel flow is metered to produce fuel-air ratios that are very close to stoichiometric for all operating conditions. Conventional IC engines are limited in compression ratio by the requirement that the fuel must be burned at stoicheometric premixed fuel-air ratios with no detonation or pre-ignition, which limits the thermal efficiency that can be achieved with these engines. Diesel engines with direct fuel injection can operate at much higher compression ratios and leaner fuel-air ratios with higher efficiency. However, diesel engines use compression ignition of fuel that is not well mixed, resulting in a significant combustion delay time and reduced release of energy at the beginning of the power stroke, which results in reduced efficiency.